Electroplating apparatus

ABSTRACT

A electroplating apparatus which is suitable for depositing a metal layer of substantially uniform thickness across the center and edge regions of a semiconductor wafer substrate is disclosed. The apparatus includes a reservoir for containing an electrolytic fluid. A cathode, to which is mounted a wafer, and an anode in the electrolytic fluid are connected to an electroplating current source. A shield is provided between the cathode and anode to facilitate a more uniform deposit of the metal onto the wafer across the entire surface, including the center and edge regions, of the wafer.

FIELD OF THE INVENTION

The present invention relates to electrochemical plating (ECP)apparatuses and processes used to deposit metal layers on semiconductorwafer substrates in the fabrication of semiconductor integratedcircuits. More particularly, the present invention relates to anelecroplating apparatus which includes a shield interposed between ananode and a cathode to reduce the electroplating deposition rate at theedge region of a substrate and facilitate deposition of a metal filmhaving a substantially uniform thickness across the entire surface of awafer.

BACKGROUND OF THE INVENTION

In the fabrication of semiconductor integrated circuits, metal conductorlines are used to interconnect the multiple components in devicecircuits on a semiconductor wafer. A general process used in thedeposition of metal conductor line patterns on semiconductor wafersincludes deposition of a conducting layer on the silicon wafersubstrate; formation of a photoresist or other mask such as titaniumoxide or silicon oxide, in the form of the desired metal conductor linepattern, using standard lithographic techniques; subjecting the wafersubstrate to a dry etching process to remove the conducting layer fromthe areas not covered by the mask, thereby leaving the metal layer inthe form of the masked conductor line pattern; and removing the masklayer typically using reactive plasma and chlorine gas, thereby exposingthe top surface of the metal conductor lines. Typically, multiplealternating layers of electrically conductive and insulative materialsare sequentially deposited on the wafer substrate, and conductive layersat different levels on the wafer may be electrically connected to eachother by etching vias, or openings, in the insulative layers and fillingthe vias using aluminum, tungsten or other metal to establish electricalconnection between the conductive layers.

Deposition of conductive layers on the wafer substrate can be carriedout using any of a variety of techniques. These include oxidation, LPCVD(low-pressure chemical vapor deposition), APCVD (atmospheric-pressurechemical vapor deposition), and PECVD (plasma-enhanced chemical vapordeposition). In general, chemical vapor deposition involves reactingvapor-phase chemicals that contain the required deposition constituentswith each other to form a nonvolatile film on the wafer substrate.Chemical vapor deposition is the most widely-used method of depositingfilms on wafer substrates in the fabrication of integrated circuits onthe substrates.

Due to the ever-decreasing size of semiconductor components and theever-increasing density of integrated circuits on a wafer, thecomplexity of interconnecting the components in the circuits requiresthat the fabrication processes used to define the metal conductor lineinterconnect patterns be subjected to precise dimensional control.Advances in lithography and masking techniques and dry etchingprocesses, such as RIE (Reactive Ion Etching) and other plasma etchingprocesses, allow production of conducting patterns with widths andspacings in the submicron range. Electrodeposition or electroplating ofmetals on wafer substrates has recently been identified as a promisingtechnique for depositing conductive layers on the substrates in themanufacture of integrated circuits and flat panel displays. Suchelectrodeposition processes have been used to achieve deposition of thecopper or other metal layer with a smooth, level or uniform top surface.Consequently, much effort is currently focused on the design ofelectroplating hardware and chemistry to achieve high-quality films orlayers which are uniform across the entire surface of the substrates andwhich are capable of filling or conforming to very small devicefeatures. Copper has been found to be particularly advantageous as anelectroplating metal.

Electroplated copper provides several advantages over electroplatedaluminum when used in integrated circuit (IC) applications. Copper isless electrically resistive than aluminum and is thus capable of higherfrequencies of operation. Furthermore, copper is more resistant toelectromigration (EM) than is aluminum. This provides an overallenhancement in the reliability of semiconductor devices because circuitswhich have higher current densities and/or lower resistance to EM have atendency to develop voids or open circuits in their metallicinterconnects. These voids or open circuits may cause device failure orburn-in.

A typical standard or conventional electroplating system 10 fordepositing a metal such as copper onto a semiconductor wafer is shown inFIG. 1. The electroplating system 10 includes a standard electroplatingcell having an adjustable current source 12, a bath container 14 whichholds an electrolyte electroplating bath solution (typically acid coppersulfate solution) 16, and a copper anode 18 and a cathode 20 immersed inthe electrolyte solution. The cathode 20 includes a semiconductor wafer22 that is to be electroplated with metal. A contact ring 24 mounts thewafer 22 to the cathode 20.

Both the anode 18 and the cathode 20 are connected to the current source12 typically by means of suitable wiring 26. The electroplating bathsolution 16 may include an additive for filling of submicron featuresand leveling the surface of the copper electroplated on the wafer 22. Anelectrolyte holding tank (not shown) be may further be connected to thebath container 14 for the addition of extra electrolyte solution to thebath container 14, as needed.

In operation of the electroplating system 10, the current source 12applies a selected voltage potential typically at room temperaturebetween the anode 18 and the cathode 20. This potential creates amagnetic field around the anode 18 and the cathode 20, which magneticfield affects the distribution of the copper ions in the bath 16. In atypical copper electroplating application, a voltage potential of about2 volts may be applied for about 2 minutes, and a current of about 4.5amps flows between the anode and the cathode 20 and wafer 22.Consequently, copper is oxidized at the anode 18 as electrons from thecopper anode 18 reduce the ionic copper in the copper sulfate solutionbath 16 to form a copper electroplate on the wafer 22, at the interfacebetween the wafer 22 and the copper sulfate bath 16.

The copper oxidation reaction which takes place at the anode 18 isillustrated by the following reaction equation:Cu---->Cu⁺⁺+2 e ⁻

The oxidized copper cation reaction product forms ionic copper sulfatein solution with the sulfate anion in the bath 16:Cu⁺⁺+SO₄ ⁻⁻---->Cu⁺⁺SO₄ ⁻⁻

At the wafer 22, the electrons harvested from the anode flowed throughthe wiring reduce copper cations in solution in the copper sulfate bath16 to electroplate the reduced copper onto the wafer 22:Cu⁺⁺+2 e ⁻---->Cu

When a copper layer is deposited on the wafer 22, such as byelectrochemical plating, the copper layer must be deposited on a metalseed layer 23 such as copper which is deposited on the wafer 22 prior tothe copper ECP process. Seed layers may be applied to the substrateusing any of a variety of methods, such as by physical vapor deposition(PVD) and chemical vapor deposition (PVD). Typically, metal seed layersare thin (about 50-1500 angstroms thick) in comparison to conductivemetal layers deposited on a semiconductor wafer substrate.

Conventional electrochemical plating techniques use copper sulfate(CuSO₄) for the main electrolyte in the electroplating bath solution.The solution may further include additives such as chloride ion andlevelers, as well as accelerators and suppressors which increase anddecrease, respectively, the rate of the electroplating process. The rateof deposition of copper on the substrate, and the quality and resultingelectrical and mechanical properties of the metallization, are largelydependent on the concentration of these organic additives in theelectroplating bath solution.

However, one of the drawbacks of the conventional electroplating system10 is that the current density at the contact ring 24 is higher than thecurrent density at the central region of the wafer 22. Therefore, theplating film is thicker at the edge region than at the center region ofthe wafer 22. Thus, the thickness of the plating film electroplated ontothe wafer 22 is non-uniform. Accordingly, a novel electroplating deviceis needed to control the thickness of a metal electroplated onto theedge region of a substrate in order to facilitate a more uniformdistribution of the metal across the edge and central regions of awafer.

An object of the present invention is to provide a novel electroplatingapparatus which is suitable for the electroplating of a metal on a waferin the fabrication of integrated circuits.

Another object of the present invention is to provide a novelelectroplating apparatus which facilitates control in the thickness of ametal electroplated onto the edge region of a wafer.

Another object of the present invention is to provide a novelelectroplating apparatus which may include a mechanism to control theion density of an electroplating solution in order to control thequantity of metal electroplated onto an edge region of a wafer.

Still another object of the present invention is to provide a novelelectroplating apparatus which may include a shield positioned betweenan anode and a cathode/wafer to alter the electric pathway between thewafer and the anode and improve the thickness uniformity of a metallayer electroplated onto the wafer.

Yet another object of the present invention is to provide a novelelectroplating apparatus which may include a shield positioned betweenan anode and a cathode/wafer and a current source electrically connectedto the shield to apply a selected negative or positive voltage to theshield and adjust the concentration of metal ions in an electroplatingbath for the uniform deposit of a metal layer on the wafer.

Yet another object of the present invention is to provide a novel methodfor the uniform electroplating of a metal onto a wafer.

SUMMARY OF THE INVENTION

In accordance with these and other objects and advantages, the presentinvention is generally directed to a novel electroplating apparatuswhich is suitable for depositing a metal layer of substantially uniformthickness across the center and edge regions of a semiconductor wafersubstrate. The apparatus includes a reservoir for containing anelectrolytic fluid. A cathode, to which is mounted a wafer, and an anodein the electrolytic fluid are connected to an electroplating currentsource. A shield is provided between the cathode and anode to facilitatea more uniform deposit of the metal onto the wafer across the entiresurface, including the center and edge regions, of the wafer.

The shield may have a ring-shaped configuration or a plate-shapedconfiguration and may be either electrically non-conductive orelectrically-conductive. The electrically non-conductive shield altersthe electric pathway between the anode and cathode in the electrolyticfluid. Consequently, the distribution of metal ions in the fluid,between the shield and wafer, is changed in such a manner that thethickness of a metal layer deposited onto the wafer is substantiallyuniform across the edge and center regions of the wafer.

The electrically-conductive shield may be connected to a shield currentsource. A switch may be provided between the shield current source andthe shield. The switch may be manipulated to apply a negative charge tothe shield, in which case the shield acts as a cathode and reduces thequantity of metal cations in the electrolytic fluid in the area adjacentto the edge region as compared to the area adjacent to the center regionof the wafer. Consequently, the electroplating metal deposition rate atthe edge region is reduced to compensate for the normally lower metaldeposition rate at the center region of the wafer, thus enhancing theoverall thickness uniformity of the electroplated metal.

The switch may be manipulated to apply a positive charge to the shield,in which case the shield acts as an anode. Accordingly, theconcentration of metal cations in the electrolytic fluid in the areaadjacent to the edge region relative to the center region of the waferis increased, to increase the electroplating deposition rate of themetal onto the edge region of the wafer, as deemed necessary. By thealternating application of positive and negative charges to the waferusing the switch, the thickness of metal electroplated onto the edgeregion of the wafer can be precisely controlled to provide a layer ofelectroplated metal having a substantially uniform thickness across theentire surface of the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a schematic of a typical conventional electroplating system;

FIG. 2 is a schematic of an electroplating apparatus of the presentinvention;

FIG. 3 is a top view of a ring-shaped shield element of theelectroplating apparatus of FIG. 2;

FIG. 4 is a cross-section taken along section lines 4-4 in FIG. 3;

FIG. 5 is a schematic of another embodiment of the electroplatingapparatus of the present invention;

FIG. 6 is a top view of a plate-shaped shield element of theelectroplating apparatus of FIG. 5;

FIG. 7 is a cross-section taken along section lines 7-7 in FIG. 6; and

FIG. 8 is a schematic of still another embodiment of the electroplatingapparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention has particularly beneficial utility in theelectrochemical plating of copper or other metal onto a semiconductorwafer substrate in the fabrication of semiconductor integrated circuits.However, the invention is more generally applicable to theelectrochemical plating of metals including but not limited to copper onsubstrates in a variety of industrial applications, including but notlimited to semiconductor fabrication.

The present invention is generally directed to a novel electroplatingapparatus which enhances uniformity in the thickness of a metal layerdeposited on a semiconductor wafer. The apparatus facilitates theelectroplating of a metal layer having substantially uniform thicknessacross the entire wafer surface, particularly between the center andedge regions of the wafer. The apparatus includes a bath containerhaving a reservoir for containing an electrolytic fluid. A cathode andan anode immersed in the electrolytic fluid are connected to anelectroplating current source. The wafer is provided in electricalcontact with the cathode, in the electrolytic fluid. A shield isprovided between the cathode and anode to modify the electricalcharacteristics of the electrolytic fluid and provide a substantiallyuniform thickness of the metal electroplated onto the center and edgeregions of the wafer.

The shield may be ring-shaped or plate-shaped and may be electricallynon-conductive or electrically-conductive. In one embodiment of theapparatus, the shield is either electrically conductive ornon-conductive and alters the electric pathway between the anode andcathode in the electrolytic fluid. This alters the distribution of metalions in the electrolytic fluid in such a manner that the thickness of ametal layer deposited onto the wafer is substantially the same acrossthe edge region and center region on the wafer.

In another embodiment of the apparatus, the shield iselectrically-conductive and may be connected to a shield current source.A switch may be provided between the shield current source and theshield. When the switch is manipulated to apply a negative charge to theshield, the shield acts as a cathode and reduces metal cations in theelectrolytic fluid in the area adjacent to the edge region of the wafer.This reduces the quantity of metal cations in the electrolytic fluid inthe area adjacent to the edge region as compared to the area adjacent tothe center region of the wafer. Consequently, the electroplating metaldeposition rate at the edge region of the wafer is reduced to compensatefor the normally lower metal deposition rate at the center region of thewafer. This enhances the overall thickness uniformity of theelectroplated metal across the entire surface of the wafer.

Upon application of a positive charge to the shield by manipulation ofthe switch, the shield acts as an anode. Accordingly, the concentrationof metal cations in the electrolytic fluid in the area adjacent to theedge region of the wafer is increased, to increase the electroplatingdeposition rate of the metal onto the edge region of the wafer, asneeded. By the alternating application of positive and negative chargesto the wafer by manipulation of the switch, the thickness of metalelectroplated onto the edge region of the wafer can be preciselycontrolled to provide a layer of electroplated metal having asubstantially uniform thickness across the entire surface of the wafer.

The electroplating apparatus may further include a mechanism to controlthe relative position of the shield with respect to the wafer in theelectrolytic fluid. By movement of the negatively-charged cathode/shieldtoward the wafer, the deposition rate of the metal onto the edge regionof the wafer is reduced correspondingly. By movement of thenegatively-charged cathode/shield away from the wafer, the depositionrate of the metal onto the edge region of the wafer is increased. Thismechanism can be used in combination with the switch to facilitateprecise control of the relative thickness of metal electroplated ontothe center and edge regions of the wafer.

The electroplating apparatus of the present invention may be used withany formulation for the electrolytic fluid, such as copper, aluminum,nickel, chromium, zinc, tin, gold, silver, lead and cadmiumelectroplating baths. The present invention is also suitable for usewith electroplating baths containing mixtures of metals to be platedonto a substrate. It is preferred that the electrolytic fluid be acopper alloy electroplating bath, and more preferably, a copperelectroplating bath. Typical copper electroplating bath formulations arewell known to those skilled in the art and include, but are not limitedto, an electrolyte and one or more sources of copper ions.

Suitable electrolytes include, but are not limited to, sulfuric acid,acetic acid, fluoroboric acid, methane sulfonic acid, ethane sulfonicacid, trifluormethane sulfonic acid, phenyl sulfonic acid, methylsulfonic acid, p-toluenesulfonic acid, hydrochloric acid, phosphoricacid and the like. The acids are typically present in the bath in aconcentration in the range of from about 1 to about 300 g/L. The acidsmay further include a source of halide ions such as chloride ions.Suitable sources of copper ions include, but are not limited to, coppersulfate, copper chloride, copper acetate, copper nitrate, copperfluoroborate, copper methane sulfonate, copper phenyl sulfonate andcopper p-toluene sulfonate. Such copper ion sources are typicallypresent in a concentration in the range of from about 10 to about 300g/L of electroplating solution.

Other electrochemical plating process conditions suitable forimplementation of the present invention include a plating rpm of fromtypically about 0 rpm to about 500 rpm; a plating current of fromtypically about 0.2 mA/cm² to about 20 mA/cm²; a plating voltage oftypically about 2 volts and a bath temperature of from typically about10 degrees C. to about 35 degrees C. In cases in which planarity of theelectroplated metal through chemical mechanical planarization (CMP) isnecessary, a leveling agent may be added to the electroplating bathsolution at a concentration of from typically about 5 mmol/L to about 5mol/L.

Referring to FIG. 2, an illustrative embodiment of an electroplatingapparatus 30 of the present invention is shown. The apparatus 30 may beconventional and includes a standard electroplating cell having anadjustable electroplating current source 32, a bath container 34 havingan interior bath reservoir 35, a typically copper anode 36 and a cathode38. A contact ring 40 holds a semiconductor wafer 42 that is to beelectroplated with metal, against the cathode 38.

The anode 36 and cathode 38 are connected to the current source 32 bymeans of suitable wiring 33. The bath container 34 holds an electrolyticfluid or electroplating bath solution 44. The apparatus 30 may furtherinclude a mechanism (not shown) for rotating the wafer 42 in theelectrolytic fluid 44 during the electroplating process, as is known bythose skilled in the art.

A shield 46 is mounted in the bath container 34, beneath the contactring 40, according to techniques known by those skilled in the art. In apreferred embodiment, the shield 46 is mounted on a positionaladjustment arm 60 which is engaged by a positional adjustment motor 58.The positional adjustment motor 58 is operated to adjust the verticalposition of the shield 46 in the bath container 34, and thus, theproximity of the shield 46 to the contact ring 24.

As shown in FIGS. 3 and 4, the shield 46 typically includes aring-shaped shield body 48 having a central shield opening 50. Theshield body 48 may be an electrically-conductive metal or anon-conductive material such as plastic or ceramic, for example. In thecase of a non-conductive shield body 48, an electrically-conductivematerial 51 covers the surfaces of the shield body 48. Preferably, theelectrically-conductive material 51 is copper.

As shown in FIGS. 3 and 4, typical dimensions for the ring-shaped shield46 include a diameter 64 of typically about 150˜200 mm; a ring width 65of typically about 3˜5 cm; and a thickness 66 of typically about 30˜50mm. These dimensions are compatible with an electroplating apparatus 30which is sized for the processing of 300 mm wafers. However, it isunderstood that these dimensions may vary depending on the diameter ofwafers to be processed in the electroplating apparatus 30.

An electrical contact 52, such as suitable wiring, for example, iselectrically connected to the shield 46. A switch 54 is connected to theelectrical contact 52. The switch 54 provides selective electricalconnection between a positive terminal 56 a and a negative terminal 56 bof a shield current source 56. Accordingly, in operation of theapparatus 30 as hereinafter described, a positive charge is selectivelyapplied to the shield 46 by establishing electrical communicationbetween the positive terminal 56 a and the shield 46 through the switch54, as indicated by the phantom lines in FIG. 2. Conversely, a negativecharge is selectively applied to the shield 46 by establishingelectrical communication between the negative terminal 56 b and theshield 46 through the switch 54.

Referring to FIGS. 5-7, an alternative embodiment of the presentinvention is shown wherein an electroplating apparatus 70 includes ashield 72 having a plate-shaped shield body 74, as shown in FIGS. 6 and7. The shield body 74 may be an electrically-conductive metal or anon-conductive material such as plastic or ceramic, for example. In thecase of a non-conductive shield body 74, an electrically-conductivematerial 76 covers the surfaces of the shield body 74. Preferably, theelectrically-conductive material 76 is copper.

Referring again to FIG. 2, in operation of the electroplating apparatus30, an electrolytic fluid 44 is placed in the bath reservoir 35 of thebath container 34, with the anode 36 immersed in the electrolytic fluid44. The wafer 42, having a metal seed layer 43 deposited thereon, isattached to the cathode 38, typically using the contact ring 40, andimmersed in the electrolytic fluid 44. The electroplating current source32 is energized to apply a negative voltage to the cathode 38 and apositive voltage to the anode 36.

At the wafer 42, metal cations such as copper in the electrolyte fluid44 are reduced to form metal atoms, which are electroplated onto theseed layer 43. However, due to the presence of the contact ring 40, thecurrent density is higher in the area of the electrolyte fluid 44 whichis adjacent to the edge region of the wafer 42 than in the area of theelectrolyte fluid 44 which is adjacent to the center region of the wafer42. Consequently, the metal deposition rate is typically higher at theedge region than at the center region of the wafer 42.

To reduce the electroplating rate at the edge of the wafer 42, theswitch 54 is manipulated to establish electrical communication betweenthe shield 46 and the negative terminal 56 b of the shield currentsource 56. This imparts a negative charge to the shield 46, causing theshield to act as a cathode in the electrolytic fluid 44. Accordingly,metal cations adjacent to the shield 46 are reduced, forming metal atomsthat are electroplated onto the shield 46. The concentration of metalcations in the electrolyte fluid 44 adjacent to the edge region of thewafer 42 is therefore reduced, thus lowering the electroplatingdeposition rate of the metal onto the edge region of the wafer 42.

In the event that it is deemed necessary to increase the electroplatingrate at the edge region of the wafer 42, the switch 54 can bemanipulated to establish electrical communication between the shield 46and the positive terminal 56 a of the shield current source 56. Thisimparts a positive charge to the shield 46, causing the shield 46 to actas an anode. Accordingly, metal from the electrically-conductivematerial 51 (FIG. 4) of the shield 46 is oxidized, causing metal cationsto enter the electrolytic fluid 44. This increases the concentration ofmetal cations at the edge region of the wafer 42, thereby acceleratingthe electroplating deposition rate at the edge region of the wafer 42.

The electroplating deposition rate of metal onto the edge region of thewafer 42 can be further controlled by adjusting the proximity of theshield 46 with respect to the wafer 42. Thus, when the switch 54 appliesa negative charge to the cathode/shield 46, the electroplatingdeposition rate at the edge region of the wafer 42 can be decreased, asneeded, by moving the shield 46 into closer proximity to the contactring 40. Conversely, when the switch 54 applies a positive charge to theanode/shield 46, the electroplating deposition rate at the edge regionof the wafer 42 can be increased, as needed, by moving the shield 46into closer proximity to the contact ring 40. Positional adjustment ofthe shield 46 in the electrolyte fluid 44 is accomplished by actuationof the positional adjustment motor 58 and positional adjustment arm 60.

Referring next to FIG. 8, in an electroplating apparatus 80 of stillanother embodiment of the present invention, the electrical contact 52,switch 54 and shield current source 56 of the embodiments of FIGS. 2 and5 are omitted. The electroplating apparatus 80 includes a shield 82which is interposed between the anode 36 and the cathode 38. Theposition of the shield 82 may typically be adjusted in the electrolytefluid 44 by actuation of a positional adjustment motor 58 and positionaladjustment arm 60, as heretofore described with respect to theembodiments of FIGS. 2 and 5.

The shield 82 may be an electrically non-conductive material such asplastic or ceramic, for example. Alternatively, the shield 82 may be anelectrically-conductive material such as copper. Still further in thealternative, the shield 82 may include an electrically non-conductiveshield body (not shown) which is covered with an electrically-conductivematerial, as heretofore described with respect to the embodiment ofFIGS. 2 and 5. Furthermore, the shield 82 may have either a ring-shapedconfiguration or a plate-shaped configuration.

In operation of the electroplating apparatus 80, the shield 82 changesthe distribution of metal cations in the electrolytic fluid 44, betweenthe anode 36 and the wafer 42, in such a manner that the electroplatingdeposition rate at the edge region of the wafer 42 is slowed down tosubstantially equal the electroplating deposition rate at the centerregion of the wafer 42. Consequently, the thickness of a metal layerdeposited onto the seed layer 43 on the wafer 42 is substantiallyuniform between the edge and center regions of the wafer 42. The electrodeposition rate at the edge region of the wafer 42 can be increased, asneeded, by moving the shield 82 into closer proximity to the wafer 42 byoperation of the positional adjustment motor 58.

While the preferred embodiments of the invention have been describedabove, it will be recognized and understood that various modificationscan be made in the invention and the appended claims are intended tocover all such modifications which may fall within the spirit and scopeof the invention.

1. An electroplating apparatus comprising: a reservoir for holding anelectrolyte fluid; an anode and a cathode for holding a wafer providedin said reservoir; an electrical pathway provided between said cathodeand said anode; and a shield provided between said cathode and saidanode.
 2. The electroplating apparatus of claim 1 wherein said shieldcomprises a generally ring-shaped shield body.
 3. The electroplatingapparatus of claim 2 further comprising an electrically-conductivematerial provided on said shield body.
 4. The electroplating apparatusof claim 3 wherein said electrically-conductive material comprisescopper.
 5. The electroplating apparatus of claim 3 further comprising ashield current source electrically connected to said shield forselectively applying a negative charge to said shield.
 6. Theelectroplating apparatus of claim 2 wherein said shield body comprisesan electrically non-conductive material.
 7. An electroplating apparatuscomprising: a reservoir for holding an electrolyte fluid; an anode and acathode for holding a wafer provided in said reservoir; an electricalpathway provided between said cathode and said anode; and a shieldcomprising a generally plate-shaped shield body provided between saidcathode and said anode.
 8. The electroplating apparatus of claim 7further comprising an electrically-conductive material provided on saidshield body.
 9. The electroplating apparatus of claim 8 wherein saidelectrically-conductive material comprises copper.
 10. Theelectroplating apparatus of claim 8 further comprising a shield currentsource electrically connected to said shield for selectively applying anegative charge to said shield.
 11. The electroplating apparatus ofclaim 7 wherein said shield body comprises an electricallynon-conductive material.
 12. A method of electroplating a metal on awafer, comprising: providing a reservoir containing an electrolytefluid; providing an anode and a cathode in said reservoir; providing anelectrical pathway between said cathode and said anode; providing ashield in said electrolyte fluid between said cathode and said anode;and applying a current to said cathode and said anode.
 13. The method ofclaim 12 wherein said shield comprises a generally ring-shaped shieldbody.
 14. The method of claim 13 further comprising anelectrically-conductive material provided on said shield body.
 15. Themethod of claim 14 wherein said electrically-conductive materialcomprises copper.
 16. The method of claim 14 further comprising a shieldcurrent source electrically connected to said shield for selectivelyapplying a negative charge to said shield.
 17. The method of claim 16further comprising selectively applying said negative charge to saidshield for electroplating a metal onto said shield and applying apositive charge to said shield for releasing metal cations from saidshield into said electrolyte fluid.
 18. The method of claim 13 whereinsaid shield body comprises an electrically non-conductive material. 19.The method of claim 12 wherein said shield comprises a generallyplate-shaped shield body.
 20. The method of claim 19 further comprisingan electrically-conductive material provided on said shield body. 21.The method of claim 20 wherein said electrically-conductive materialcomprises copper.
 22. The method of claim 20 further comprising a shieldcurrent source electrically connected to said shield for selectivelyapplying a negative charge to said shield.
 23. The method of claim 19wherein said shield body comprises an electrically non-conductivematerial.
 24. The method of claim 22 further comprising selectivelyapplying said negative charge to said shield for electroplating a metalonto said shield and applying a positive charge to said shield forreleasing metal cations from said shield into said electrolyte fluid.